1. Field of the Invention
The present invention relates to telecommunications, in particular to wireless telecommunications.
2. Description of the Related Art
Wireless telecommunications systems are well-known. Many such systems are cellular, in that radio coverage is provided by a bundle of radio coverage areas known as cells. A base station that provides radio coverage is located in each cell. Traditional base stations provide coverage in relatively large geographic areas and the corresponding cells are often referred to as macrocells.
It is possible to establish smaller sized cells within a macrocell. Cells that are smaller than macrocells are sometimes referred to as microcells, picocells, or femtocells, but we use the terms femtocell or small cell generically for cells that are smaller than macrocells. One way to establish a femtocell is to provide a femtocell base station that operates within a relatively limited range within the coverage area of a macrocell. One example of use of a femtocell base station is to provide wireless communication coverage within a building.
The femtocell base station is of a relatively low transmit power and hence each femtocell is of a small coverage area compared to a macrocell.
Femtocell base stations are intended primarily for users belonging to a particular home or office. Femtocell base stations may be private access or public access. In femtocell base stations that are private access, access is restricted only to registered users, for example family members or particular groups of employees. In femtocell base stations that are public access, other users may also use the femtocell base station, subject to certain restrictions to protect the Quality of Service received by registered users.
One known type of Femtocell base station uses a broadband Internet Protocol connection as “backhaul”, namely for connecting to the core network. One type of broadband Internet Protocol connection is a Digital Subscriber Line (DSL). The DSL connects a DSL transmitter-receiver (“transceiver”) of the femtocell base station to the core network. The DSL allows voice calls and other services provided via the femtocell base station to be supported. The femtocell base station also includes a radio frequency (RF) transceiver connected to an antenna for radio communications.
Femtocell base stations are sometimes referred to as femtos.
Femtocell base stations are user-deployed base stations with a typical coverage range of tens of meters. They have extensive auto configuration and self-optimization capabilities so as to enable simple plug-and-play deployment, and are designed to automatically integrate themselves into an existing macrocellular network. In addition, femtos may include some functionality traditionally provided by a core network, namely a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN). One example of a femto is a UMTS Base Station Router (BSR), where UMTS denotes Universal Mobile Telecommunications System (UMTS), which integrates some functionality of a UMTS base station (NodeB), a Radio Network Controller (RNC), SGSN and GGSN.